| 1 | // -*- Mode: C -*-
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| 2 | //
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| 3 | // Cforall Version 1.0.0 Copyright (C) 2022 University of Waterloo
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| 4 | //
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| 5 | // The contents of this file are covered under the licence agreement in the
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| 6 | // file "LICENCE" distributed with Cforall.
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| 7 | //
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| 8 | // barrier.hfa -- simple barrier implemented using a monitor
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| 9 | //
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| 10 | // Author : Peter A. Buhr
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| 11 | // Created On : Sun Nov 10 08:07:35 2024
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| 12 | // Last Modified By : Peter A. Buhr
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| 13 | // Last Modified On : Wed Nov 13 12:37:04 2024
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| 14 | // Update Count : 9
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| 15 | //
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| 16 |
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| 17 | #pragma once
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| 18 |
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| 19 | #include <monitor.hfa>
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| 20 |
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| 21 | // Plan 9 inheritance does not work with monitors. Two monitor locks are created.
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| 22 |
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| 23 | monitor barrier {
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| 24 | unsigned int group, arrivals; // group size, arrival counter
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| 25 | condition c; // wait for group to form
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| 26 | };
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| 27 |
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| 28 | static inline void ?{}( barrier & b, unsigned int group ) {
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| 29 | b.group = b.arrivals = group; // arrivals count backward
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| 30 | }
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| 31 |
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| 32 | // Returns a value indicating the reverse order the threads arrived, i.e. last thread returns 0 (and does not block)
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| 33 | // last is an optional hook that is called by the Gth thread before unblocking the other threads.
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| 34 | static inline unsigned int block( barrier & mutex b, fptr_t last = (fptr_t)0 ) with( b ) {
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| 35 | arrivals -= 1; // prefix decrement so last is 0 not 1
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| 36 | unsigned arrived = b.arrivals; // note arrival order
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| 37 | if ( arrivals != 0 ) { // wait for group to form
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| 38 | wait( b.c );
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| 39 | } else { // group formed
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| 40 | if ( last ) last(); // safe to call
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| 41 | signal_all( c ); // unblock group
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| 42 | arrivals = group; // reset
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| 43 | } // if
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| 44 | return arrived; // return arrival order
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| 45 | }
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